Heat pump water heater



Dec. 7, 1954 w RUFF HEAT PUMP WATER HEATER Filed March 51, 1952 g] ivPRESSURE REDl/G /NG DEV/CE HOT WATER COLD WA TER INVENTOR A L ONZ o W.RUFF ATTORNEY United States Patent HEAT PUMP WATER HEATER Alonzo W.Ruff, York, Pa., assignor to V. C. Patterson & Associates, Inc., York,Pa., a corporation of Pennsylvania Application March 31, 1952, SerialNo. 279,703

5 Claims. (Cl. 62-4) This invention relates to heat pumps and moreparticularly to water heaters of the domestic type which operate on theheat pump principle.

Apparatus of this general type embodies basically, a hot water storagetank and a heat pump of the type in which a refrigerant is used as theworking fluid. The heat pump itself includes a motor driven compressor,an evaporator and a condenser. The evaporator is placed in a convenientlocation where it is exposed to a source of heat and the condenser isdisposed within the hot water storage tank. In operation, the compressorserves to withdraw gaseous refrigerant from the evaporator and compressthe gaseous refrigerant thereby further raising its heat content. Thehot gaseous refrigerant is then pumped through the condenser where it ischanged back to liquid phase giving up its superheat, if any, plus itslatent heat of condensation to the water in the tank. From this pointthe liquefied refrigerant is led through an expansion device to theevaporator and the cycle is repeated.

The apparatus described herein embodies several improvements over knowndevices of this type.

In general, the objects of this invention are to provide a heat pumpwater heater of improved design and operating efficiency.

The basic improvement to be described in detail herein involves a novelrefrigerant circuit for the heat pump, in which a motor compressor unithaving both a high discharge pressure and low discharge pressure outletis used. The heat exchanger condenser is divided in three sections. Onesection is positioned in the upper portion of the hot water storagetank, a second is positioned substantially in the mid-section of thetank, and the third is located in the lower portion of the tank.

The invention may be readily understood from the following descriptionread in conjunction with the accompanying sheet of drawings, in which:

The singl vfigure shows in diagrammatic form the basic refrigerantcircuit, and arrangement of the apparatus.

Referring now to the drawing, the apparatus comprises essentially arefrigerant evaporator unit 10, a hot water storage tank 11, a motorcompressor unit 12, and a con denser type heat exchanger. The evaporatormay be mounted on the tank as shown, or it may be placed in anyconvenient location where it is in heat exchange relation with a sourceof heat. Conveniently, the source of heat may be a source otherwisewasted, such as waste heat from a cooking stove or chimney flue. In caseof the former, the evaporator serves to cool and dehumidify the kitchenand in the latter case, the dehumidifying action is a desirable one inan otherwise damp basement. The heat exchanger includes a desuperheatingcoil 13 arranged in the upper part of the storage tank 11, a hightemperature condenser 14 arranged at about the mid portion of the tank,and a low temperature condenser 15 located in the lower portion of thetank. The bottom of the low temperature condensing coil is connected tothe evaporator unit by a conventional liquid line 16 in which isinterposed an expansion valve 17. The latter may be of any of severalwell known types, such as, for example, a thermally controlled expansionvalve. A suction line 18 connects the other side of the evaporator unit10 to a suction inlet on the motor compressor unit WhlCl'l inlet iscommon to both cylinders.

The compressor unit itself in accordance with the present invention,comprises a pair of cylinders 19 and 20, the former being a highdischarge pressure cylinder, and

the latter being a relatively low discharge pressure cylinder. A line 21connects the high discharge pressure cylinder 19 to the input side ofthe desuperheating coil 13 and a similar line 22 connects the output ofthe low discharge pressure cylinder 20 to the input side of the lowtemperature condensing coil 15. The low temperature condenser istherefore fed jointly by the discharge from the high temperaturecondenser coil and the discharge from the low discharge pressurecylinder 20. A pressure reducing device 23 is interposed between thehigh and low temperature condensing coils above the point where the line22 connects the low discharge pressure cylinder to the low temperaturecondenser. This serves to maintain a pressure differential between thehigh and low temperature condensing stages. In practice, the pressurereducing device may assume any one of several well known forms. Forexample, it may be a capillary tube, a spring loaded relief valve, oreven a hand adjustable throttle valve.

In order to control the rate of transfer of heat to the water in thetank, a thermostat 24 may be located substantially at the mid-section ofthe storage tank in heat exchange relation to the water in the tank atthat point, and is connected in series with the source of electricalsupply to the motor compressor unit. A fan 25 driven by an electricmotor 26 maintains a fiow of air over the evaporator unit 10, and themotor 26 is connected in parallel with the motor of the motor compressorunit so that it also will be controlled by the thermostat 24-.

In operation, therefore, inresponse to a demand for heat in the storagetank, the thermostat 24 operates to close the circuit to the motorcompressor unit 12 and the fan motor 26. The motor compressor unit thensupplies superheated refrigerant to coil 13 and simultaneously suppliesheated gaseous refrigerant at a relatively lower temperature andpressure to the heat exchange coil 15. The refrigerant in coil 13 losesits superheatto the water in the upper portion of the tank and thenflows, as a saturated gas, down to the high temperature condenser whereit is partially condensed, and part of the latent heat of condensationis transferred to the water in the mid-section of the tank. The mixtureof gas and liquid after passing through the pressure reducing device,then joins the heated gas from the low pressure cylinder. The resultingmixture is then circulated through the low temperature condenser coil 15to give up the remainder of its latent heat of condensation to the waterin the lower portion of the tank. From there, the cooled and liquefiedrefrigerant passes through the liquid line 16, the expansion valve 17and into the evaporator unit 10. There, in changing back from liquid togaseous state, it picks up heat from the ambient air being circulatedthrough the evaporator coils by the fan 25. The heat laden refrigerantis then returned to a common intake of the motor compressor unit throughthe suction line 18, where it is recompressed and the cycle is repeated.

It has been discovered that the basic refrigerant circuit as describedabove yields superior results, as to operating eificiency. While thecompressor shown on the attached drawing is of the piston type, it willbe apparent to those skilled in the art that other well known types,such for example as rotary compressors, are readily adaptable to theapparatus herein shown and described. Also, a compressor having morethan two difierent discharge pressure outlets could be used. Forexample, a compressor having three diiferent discharge pressure outletscould be used to feed separately, the three stages of the heatexchanger.

In addition, however, to the above described refinements in therefrigerant circuit, it has also been discovered that the waste heat ofthe motor compressor unit may be more effectively utilized by increasingits rate of transfer to the water in the tank. This is accomplished bycertain structural modifications, a description of which follows.

Referring again to the drawing, it will be seen that the storage tank 11is provided with a depression or pocket 27 in a side wall of the tankadjacent the upper end thereof. In practice, the motor compressor unitwill be of the well known hermetically sealed type, but it in turn willbe wholly received within the pocket 27 and also sealed therein. Thespace intermediate the motor compressor unit and the pocket is thenfilled with a non inflammable liquid having good heat transfercharacteristics in order to increase the rate of transfer of the wasteheat from the motor compressor to the warmest Water in the upper portionof the tank by conduction. One ex ample of a liquid Well adapted to thispurpose is Pyranol, which is a well known oil, in common use, inoilimmersed electrical transformer apparatus. it also has highdielectric constant which is desirable to prevent short circuiting theelectrical leads which carry current to the motor compressor unit.

The water in the storage tank of heaters of this type tends to stratifyin definite temperature levels. The hottest water will be in the upperportion of the tank surrounding the desuperheating coil, while the waterin the bottom portion of the tank surrounding the low temperaturecondenser coil may be only a few degrees warmer than the make up water.The water in the mid-section of the tank, surrounding the hightemperature condenser will be at an intermediate temperature and thesetemperature strata remain fairly constant in normal operation of theapparatus. For this reason, the operating characteristics of the heatexchanger, that is, its temperature and pressure in the three sections,also remain substantially constant.

The foregoing will enable one skilled in the art to fully understand theinvention and the novelty thereof which is defined by the followingclaims.

I claim:

1. A water heater of the heat pump type, comprising in combination: ahot water storage tank; a refrigerant evaporator adapted to absorb heatfrom the atmosphere; heat transfer means of the type in whichrefrigerant is circulated, said means being disposed in heat exchangerelation to the water in said tank, extending substantially from top tobottom thereof and including during normal operating conditions, adesuperheating stage located adjacent the upper part of said tank, ahigh temperature condensing stage located substantially at themid-section of said tank, and a low temperature condensing stage locatedadjacent the bottom part of said tank said stages being connected inseries; means connected between said high and low temperature stages tomaintain a controlled pressure differential therebetween; meansconnecting said low temperature condensing stage to said evaporator,said means including an expansion device; motor driven refrigerantcompression means, said means including at least a low dischargepressure outlet and a high discharge pressure outlet; a common suctioninlet for said compression means; means connecting said high dischargepressure outlet to said desuperheating stage; means connecting said lowdischarge pressure outlet to said low temperature condensing stage;means connecting said evaporator to the suction inlet of saidcompressor; and means responsive to the temperature of the water in saidtank to control the transfer of heat thereto.

2. A water heater of the heat pump type, comprising in combination: ahot Water storage tank; a refrigerant evaporator adapted to absorb heatfrom the atmosphere; heat transfer means of the type in whichrefrigerant is circulated, said means being disposed in heat exchangerelation to the water in said tank, extending substantially from top tobottom thereof and including during normal operating conditions, adesuperheating stage located adjacent the upper part of said tank, ahigh temperature condensing stage located substantially at themid-section of said tank, and a low temperature condensing stage locatedadjacent the bottom part of said tank said stages being connected inseries; means connected between said high and low temperature stages tomaintain a controlled pressure differential therebetween; meansconnecting said low temperature condensing stage to said evaporator,said means including an expansion device; a motor compressor unit, saidcompressor including a low discharge pressure cylinder and a highdischarge pressure cylinder; a suction inlet to said compressor commonto both said cylinders; means connecting said high discharge pressurecylinder to said desuperheating stage; means connecting said lowdischarge pressure cylinder to said low temperature condensing stage;means connecting said evaporator to the suction inlet of saidcompressor; and means responsive to the temperature of the water in saidtank to control the transfer of heat thereto.

3. A water heater as defined by claim 1 in which the motor compressorunit is mounted on and in heat exchange relation to said storage tank.

4. A water heater as defined by claim 1 in which said storage tank isformed with a depressed pocket in the side wall thereof adjacent theupper portion thereof; means sealing said motor compressor unit withinsaid pocket; and a noninfiammable liquid having a high dielectricconstant interposed in the space intermediate said compressor unit andsaid storage tank to increase the rate of heat transfer from said motorcompressor to the water in said tank.

5. In a water heater of the heat pump type, a heat pump comprising: amotor compressor unit, said compressor including a low dischargepressure cylinder and a high discharge pressure cylinder; a suctioninlet to said compressor common to both said cylinders; an evaporator; acondenser type heat exchanger; conduit means connecting the highdischarge pressure cylinder of said motor compressor unit to one end ofsaid heat exchanger; conduit means including an expansion deviceconnecting the opposite end of said heat exchanger to said evaporator;conduit means connecting the low discharge pressure cylinder of saidmotor compressor unit to an intermediate point on said heat exchanger;means connected to said heat exchanger for maintaining a controlledpressure differential between that portion of the heat exchanger towhich the high discharge pressure cylinder is connected and that portionto which the low discharge pressure cylinder is connected; and furtherconduit means connecting said evaporator to the suction inlet of saidmotor compressor.

References Cited in the file of this patent UNITED STATES PATENTS

